There has been known an IC card which as not contact terminals for receiving signals from an external device or for outputting signals thereto via a magnetic or capacitive coupling therewith. When using the non-contact type IC card, as compared with the card achieving communications of signals via contact terminals, the read operation is facilitated since, for example, when a person having the card in his or her hand approaches the external device, data stored in the card can be read therefrom into the external device. Moreover, there can be prevented such problems associated with the card achieving input and output operations of data via contact terminals as a contact failure due to dirt, erosion, etc. of terminal contact points and wrong operations due to a leakage current.
For the read operation of the non-contact type IC card, the card bearer having the card with him or her need only approach the reader and there is unnecessitated a read operation to insert the card into the reader. Consequently, the card is suitable for a check of sequential passage of many persons, for example, the card is suitably used as a commuter pass or a key for checking entrance an exit for a particular room.
In a case where the non-contact type IC card is adopted as a commuter pass or a key for checking entrance and exit for a room, ID data is read from a memory of the IC card for a collation thereof such that when the collation results in a coincidence, the passage of the gate or the entrance for the room is admitted. At the same time, historical data of uses of the IC card is written in the memory thereof.
When a non-contact type IC card is brought into an area accessible to the reader-writer, the collation and the write operation of the history are accomplished. Since the accessible area has a range of a certain magnitude, when the card is employed as, for example, a commuter pass, there may occur depending on actions of the card holder a case where an identical card enters two or more times the area accessible to the reader-writer installed at the gate. Namely, it may possible occur, the user puts the card into the area, removes the card from the area, and then puts again the card into the area. In such a case, it is necessary to avoid the write operation of history in the second access.
Conventionally, in the case above, the second access of an identical card is detected by the reader-writer to inhibit the write operation of new data on the card. However, since passage of many cards is required to be checked in a short period of time at the gate, it is necessary for the reader-writer, after an access of a card, to wait for passage of a subsequent card. Consequently, there does not exit any marginal time enough to check the second access.
In consequence, it is desired that the operation of a card is inhibited for a fixed period of time after a passage thereof. However, in a card not having a power source therein, namely, a card of an external power supply type, an electromagnetic energy supplied from an external device is rectified to obtain a direct-current (dc) voltage necessary for an internal circuit thereof. Consequently, after the external energy supply is interrupted, it is difficult to control the operation inhibition for a fixed period of time. For example, after the external energy supply is stopped, the circuit in the card may be operated by energy resultant from discharge of electric charges accumulated in a smoothing capacitor of the power source circuit. However, since the operation of the circuit is determined by a value of a current consumed by the circuit and the energy accumulated in the smoothing capacitor, it is difficult to set the period for inhibiting the operation.
Moreover, in such a non-contact type IC card, since the contact (approaching) state between the card and the reader-writer cannot be fixedly established, communications of data and power source become to be unstable in some cases. For example, in a card of the external power supply type which receives supply of power via energy such as an electromagnetic field from an external power source, the card is supplied with power only when the card is in the proximity of the reader-writer. When the card is apart from the reader-writer, the power is not supplied thereto. In consequence, in a case where the bearer of the card puts the card close to the reader-writer to write data received from the reader-writer in the memory of the card, when the contact state is changed because the distance between the card and the reader-writer is increased due to movement or the like of the bearer, the power supply from the reader-writer to the card is interrupted. Consequently, the write operation of data in the memory of the card is stopped at an intermediate point and hence data is stored in the memory in an incomplete state.
Since such incomplete data is directly stored in the memory, when the data is read therefrom by the reader-writer, it is impossible to accomplish a predetermined check operation. For example, when the card is adopted as a commuter pass, the states of the pass such as a period thereof, a valid period thereof, a station name where the bearer took the train, and time when the bearer took the train are required to be accurate in any case. Otherwise, there arises a problem that the essential object of the card cannot be achieved.
It is therefore an object of the present invention to provide a non-contact type IC card guaranteeing the normal operation even when an abnormality occurs in an access operation between the card and the external device, thereby solving the problems of the non-contact type IC card.
Namely, the present invention aims at providing a non-contact type IC card capable of preventing inappropriate data from being written therein even when the card enters an area accessible to the external device for a plurality of times at a short interval of time.
Moreover, another object of the present invention is to provide a non-contact type IC card guaranteeing the normal operation even when an abnormality occurs in the contact state during a write operation of data from the external device.